Yeah, the numbers and letters are supposed to be lit up at night. Its more likely that the plug is loose. You can get to it by pulling out the ashtray. If you don't see it, taking off the plastic center stack cover is as simple as a couple of screws under the cupholders, one behind the ashtray, and some clips or something at the top near the clock.

If the plug is loose, just wiggling it may be enough to get the lights to come back on under PRND4D321.